Protective device for walking beam pumping rigs



March 21, 1933. DA SB 1,902,492

PROTECTIVE DEVICE FOR WALKING BEAM PUMPING RIGS Filed Sept. 24. 1950 Invent or Harry H Dansboe,

His Attorne g.

Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE HARRY H. DANSIBOE, OF DALLAS, TEXAS, ASSIGNOR TO GENERAL ELECTRIC COMPANY,

' A CORPORATION OF NEW YORK PROTECTIVE DEVICE FOR WALKING BEAM PUMPING RIG-S Application filed September 24, 1930. Serial No. 484,224.

My invention relates to protective devices for counterbalanced walking beam operating mechanism such as are commonly used in oil well pumping rigs and has for its object to shut off the operating power whenever the normal balance of the walking beam is disturbed.,

In oil well pumping service, one end of the walking beam carries the rods which extend hundreds or thousands of feet down the well casing to operate the pump, while the other end of the beam is connected by a pitman to the operating crank arm, which is suitably connected to be driven by an electric motor, gas engine, or other form of motive power. A counterweight either carried directly on the walking beam or associated with the rotating crank-arm is employed to equalize to a more or less degree the forces .20 set up Clurin the upward and downward pumping stro e. This permits the use of an electric driving motor of a size and power which without the counterweight might be entirely incapable of raising the full weight of the rods.

However, with the counterbalanced walking beam oil well pumping rig, serious difiiculties have been experienced in case the rods break or part. When this occurs, the walking beamis no longer balanced and the driving motor can not continue operation of the unbalanced walking beam without danger both to the motor itself and to the walking beam mechanism.

Where the pumping rig must be frequently started and stopped, the current overload protective device for the electric motor ordinarily is set to function only at a value of current in excess of the motor starting current which may be much more than the safe continuous load current of the motor. Thus when the unbalance of the walking beam occurs due to parting of the rods, the overload current of the driving motor may not be 5 sufficient to trip out the current overload protective device but still be ofa. dangerous continuous load value. As a result the motor winding may gradually become overheated and the insulation destroyed and thereby eventually cause a burn-out of the motor.

This is particularly true with a variable speed motor where the speed controller is set for slow speed operation of the motor.

Likewise with the walking beam mechanism unbalanced by the parting of the rods, the unbalanced forces set up in the mechanism in case the motor continues to run may produce strains that would result in breakage of the various parts or overloading and burning out of the bearings or in other similar mechanical difficulties.

In accordance with the present invention the protection of the walking beam pumping rig against the difiiculties noted above is obtained, not in accordance with overload current of the driving motor but in response to the unbalanced condition of the walking beam mechanism itself. I have discovered that whenever the normal balance of the walking beam is disturbed as by breaking or parting of the rods, there is a material variation in the path of movement of the walking beam from that occurring during normal counterbalanced operation thereof. Hence I provide means responsive to the abnormal unbalanced movement of the walking beam and arranged automatically to shut off the operating power whenever such movement occurs.

In carrying the invention into eflect in a preferred form, a. movable member is mounted adjacent the path of normal movement of the walking beam so as to be engaged thereby upon abnormal, unbalanced movement thereof. I associate a switch or other suitable circuit controlling means with the movable member, so as to be operated thereby to interrupt the power circuit of the driving motor whenever the abnormal unbalanced operation of the walking beam occurs.

In the accompanying drawing Fig. 1 is a schematic diagram showing a preferred form of protective device applied to an electric motor driven counter-balanced Walking beam oil well pumping rig and Fig. 2 shows the protective device applied to a gas engine drive for the pumping rig.

In the drawing the walking beam 10 is pivotally mounted intermediate its end on the Sampson post 11. The right-hand end of the walking beam 10 carries the fitting 12 which holds the string of rods 13 extending down the well tubing and casing 14 to the pump which may be located many hundreds or thousands of feet below the surface of the grounchdepending upon the particular depth at which. the oil is encountered. The lefthand end of the walking beam 10 is connected through the pitman 15 to the crank arm 16, which 'a's'indicatcd diagrammatically in the drawing is driven by the multi-phase electric motor 17 through the agency of the belt 18 and pulleys 19 and 20.

The left-hand end of the walking beam 10 also carries the counter-weight 21, which is of a mass sufiicient to almost equal. the weight of the rods 13 extending down the casing 14:. However, no downward push upon the rods 13 such as might cause buckling and breaking thereof is permissible, and the force required for the downward stroke of the pump, must be produced from the weight of the rods themselves. Thus the pitinan 15 is required only to lift the excess weight of therods 13 and oil over the counter-weight 21, and never exerts any downward force on the rods themselves. For this there is considerablelost motion permissible in the connection of the pitman 15 with the walking beam 10 as well as with the crank-arm 16, all of which, for the purpose of simplicity is indicated by the slot 22 in the end'of the pitman 15 which engages with the pin 23 carried by the walking beam.

The electric driving motor is shown as of the polyphase induction type having the adjustable speed regulating resistors 30 connected in the secondary circuit thereof. Power is applied to the motor 17 from a suitable s'ource through the 3 phase circuit breaker 31. The circuit breaker 31 is shown diagrammatically as held in the closed position under the control of the under voltage magnet 32, which is energized from the potential transformer 33. The under voltage electromagnet 32 operates upon the latch 34, which latch is spring biased to release the circuit interrupter 31,so as to hold the latch 34 against this bias and thereby maintain the circuit interrupter 31 in the closed position.

In order to eifect opening of the circuit breaker 31 upon the occurrence of unbalanced movement of the walking beam 10 and thereby interrupt the circuit of the driving motor, the protective device 35 is provided. This device as shown diagrammatically in the drawing, consists, of the movable lever arm 36 which is pivotally mounted intermediate its end in the adjustable bracket 37 so that the right-hand end of the arm 36 may be lo cated adjacent to the path of normal counterbalanced movement of the walking beam 10. The left-hand end of thelever arm 36 engages with the switch member 38 which, as shown,

is connectedin the energizing circuit of the undervoltage electromagnet 32. The contact 38 is biased to the open position by the spring 39. A stronger spring 40 acting upon the operating lever arm 36, however, serves normally to maintain the contact 38 in the closed position as shown. Whenever the righthand end of the lever arm 36 is engaged by the walking beam 10, the force of spring 40 is removed from the contact 38 and the latter is thereupon opened by operation of the spring 39. The length of the adjustable pin ll extending between the switch contact 38 and the arm 36 be varied so as to adjust the positionofthe right-hand end of the arm 36 closely adjacent to the normal path of the walking beam 10. i The operation of the arrangement shown and described above, is as follows. With the circuit breaker 31 closed, the motor 17 is energized and through the agency of the belt 18, and the pulleys 19 and 20 serves to drive the crank arm 16. The latter, through the pitman-15 operates upon its downward throw to lower the'left-hand end of the walking beam 10, and thereby raise the pump rods 13 while the weight of the rods 13 serves to produce the downward stroke of the pump upon the upward throw of the crank arm 16. The resistors 30 maybe varied, in order to vary the speed of the operating motor 17 to produce the proper pumping eifect. Under normal operating conditions, the lever arm 36 is adjusted by means of the adjustable bracket 37 and also the adjustable pin 41 so as to occupy a position just beyond the nor mal down stroke of the left-hand end of the walking beam 10.

Whenever the rods 13 break or part so as to leave the counter-weight 21 on the lefthand end of the walking beam 10 materially in excessoftheweight of the rods 13 on the right-hand end thereof, the lostmotion in the various bearings represented by the slot 22 in the end ofthe pitman 15 as well as the yield in the walking beam, the supporting sills etc. of'the pumping rig permits an abnormal unbalanced movement of the walk ing beam into engagement with the righthand end of the lever arm 36. Under these conditions the left-hand end of the arm 36 is raised and the spring 39-serves to open the switch contact 38. This interrupts the circuit of the under voltage electromagnet 32, and thereby permits'thespring biased latch 34 to release the circuit interrupter 31. Upon the opening of the circuit interrupter 31, the driving motor 17 is de-energized and the pumping rig shut down;

As soon as the rods have been repaired and the walking beam 10 restoredto its normal counter-balanced condition, the circuit inter rupter 31 may be again closed to continue operation of the driving motor 17. It should be noted that in case of excessive unbalanced movementof the walking beam 10, no injury images can occur to the switch 238 or the parts of'ithe operating lever arm 36, since the lever arm is free .to move away from engagement with the adjustable pin 41 any amount depending upon the movement imported thereto by the excess movement of the left-hand end of the walking beam 10.

As shown in Fig. 2, the protective device 35 is applied to control the ignition circuit of a gas engine 50, which may be connected to drive the counterbalance walking beam pumping rig of Fig. 1 in place of the electric motor 17. In this case the contact 38 of the protective device is connected in the circuit between the magneto 51 and the spark plug 52 of the gas engine. Consequently, when the normal balance operation of the walking beam 10 is disturbed by parting of the rods, the end of the beam 10 engages with the member 36 to remove the bias of the binding spring 40, and thereby permit the spring 39 to open the contact 38 and in this way cut off the ignition to stop the gas engine. This use of the protective device 35 prevents continued thrashing of the unbalanced walking beam with possible: injury or destruction of the pumping rig due to unbalanced operation thereof.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A protective device for a motor driven counter-balanced walking beam pumping rig comprising a switch for controlling the energizing circuit of the electric driving motor, electro-responsive means for maintaining said switch in the closed position, a control switch for controlling the energization of said electro-responsive means, and a member adapted to be positioned adjacent the normal path of movement of a movable part of the beam mechanism to be engaged thereby upon abnormal unbalanced movement of the beam mechanism and arranged to control said electric switch.

2. A protective device for a motor driven counter-balanced walking beam pumping rig comprising a switch for controlling opera tion of said motor, said switch being biased to open to stop said motor, a lever biased to hold said switch in the closed position to maintain said motor energized, said lever being positioned adjacent the path of movement of a movable part of the beam mecl1anism to be engaged thereby upon abnormal unbalanced movement thereof, said lever permitting said switch to move to open position to deenergize said motor when said lever is moved against its bias by the movable part of said beam mechanism.

3. A protective device for a gas engine driven counter-balanced walking beam pumping rig, an ignition system for said gas engine, a switch for controlling said ignition system, a lever biased to hold said switch member in closed position to maintain said ignition system energized, said lever being adapted to be positioned adjacent the normal path of movement of a movable part of the beam mechanism to be engaged thereby upon abnormal unbalanced movement of the beam, said lever causing said switch to open to deenergize said ignition system to stop said gas engine when the movable part of the beam mechanism contacts with said lever.

4. A protective system for a motor arranged to drive a counterbalanced walking beam between predetermined limits comprising a switch for controlling the energizat on of said motor, a normally open switch, an operating member for said switch normally biasing said switch to its closed position, and means pivotally mounting said member in the path of movement of said beam, said member being arranged to be engaged by the 7 beam upon abnormal operation thereof thereby to release said switch for operation to its open position.

5. In combination a walking beam, a fulcrum at its mid portion and hav ng a load connected to said beam on one side of the fulcrum, a counterbalancmg load on the other side of sald fulcrum, a driving motor connected to said beam for osclllating said beam over its fulcrum through predetermined limits, of means for deenergiz ng said motor on the occurrence of movement of said beam beyond said limits comprising a normally open switch for controlling the energization of said motor, an operative member arranged in cooperative relation with sa d switch for maintaining it closed and means mounting said member in the path of said beam arm and slightly beyond one of its limits of movement so as to be engaged by said beam arm upon abnormal movement thereof to open said switch, said member for further abnormal movement of said beam arm being ar ranged for movement independently of said switch.

6. In combination, an electric motor ar ranged to drive a pumping rig, a walking beam having its respective ends connected to said motor and to said pump ng rig, a switch for controlling the operation of said electric motor, means normally biasing said switch to a position to stop the motor, a movable member in abutting relation with said switch and biased to hold sa d switch in a second position for maintaining the electric driving motor in operation and mounting means for said member for adjustably positioning it in the path of movement of said beam. so as to be operated to release sa d switch for operation. to said position to stop said motor.

7. In combination, a walking beam, a fulcrum at its mid portion and having a load connected to said beam to one side of the fulcrum and a counterbalancing load on the other side of said fulcrum, a driving motor connected to operate said beam through a predetermined movement and havinga capacity only sufficient to operate saidbeam against a predetermined unbalanced weight, of means for protecting said motor against overload due to the'loss of a substantial portion of said load comprising a control means for controlling the energization of sa d mo tor, an operating arm for said control means and means supporting said operating arm adjacent said counterbalanced end of said beam so that said control means is actuated to deenergize said motor in response to abnormal movement of said beam caused by said counterbalancing load.

8. In combination, a walking beam pivoted at its mid portion and having a load con nected at one end thereof, a counterbalancing weight for said load arranged on the opposite end of said beam, driving means for oscillating said beam between predetermined limits and means respons ve to a predetermined movement of said beam beyond one of said limits for shutting down said driving means, comprising a control circuit forsaid driving means, a SWEtCll mcluded in said circuit and an operating member for said switch positioned slightly beyond one of the normal limits of movement of one end of said beam so as to be engaged by said end to open said 9. In combination, a walking beam, a post pivotally supporting said beam at its mid portion, a load connected'to said beam on one side of said post, a counter-balancing weight on the other side of said post, a driving motor connected to said beam for operating it between predetermined limits, of a switch for protecting said motor against loss of said voltagecomprising a coil for maintaining said switch closed, an energizing circuit for said coil including a stationary contact and a movable contact, an operating lever normally maintaining said contacts closed, supporting means for maintaining said lever in the path of said beam and slightly beyond one of said limits so as-to be engaged by the beam upon an abnormal movement thereof due to fiexure of said beam and said post to deenergize said motor. I

10. A protective system for a motor arranged to drive the counterbalanced walking beam between predetermined limits comprising a switch for controlling the energization of said motor, an undervoltage electroresponsive means for opening said switch upon a predetermined drop of voltage on said motor and means responsive to the movement of.

said beam beyond one of said limits for operating said electro-responsive means to open said switch and thereby bring said motor to a standstill.

11. In combination, a walking beam pivoted at its mid-portion and having a load connected, at one end thereof, a counter-balancing'weight for said load arranged onthe opposite end of said beam, driving means for oscillatingsaid'beam only through predetermined limits, means responsive to a predetermined movement of said beam beyond one of said limits for shutting down said driving means, an operating member for said means positioned slightly beyond one of said normal limits of movement of one end of said beam so as to be engaged by said end 

